Intelligent Math Puzzle – Challenge 92

Intelligent Math Puzzle - Challenge 92 is a multiple-choice math challenge from Effortless Math. Read the problem, choose from the answer options below, then open the solution to see the full step-by-step working and check your reasoning against it.

Some Math puzzles like the following one stumped even the smartest people. Can You Solve It? The solution is also given.

Intelligent Math Puzzle – Challenge 92

Challenge:

If A and B are integers and (frac{1}{B}=frac{1}{A}-frac{1}{20}) what is the value of A+B?

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The correct answer is 9.

(frac{1}{B} =frac{1}{A} -frac{ 1}{20})
Therefore, A is less than B. Why?
Plug in different values for A.
Let’s begin with 2. If A (= 2 → frac{1}{B} = frac{ 1}{2} – frac{ 1}{20} → frac{ 1}{B} = frac{ 9}{20} → 9B = 20)
B is an integer. Therefore, B cannot be (frac{ 20}{9})
A (= 3 → frac{ 1}{B} = frac{ 1}{3} – frac{ 1}{20} → frac{ 1}{B} = frac{ 17}{60} → 17B = 60)
A (= 4 → frac{ 1}{B} = frac{ 1}{4} – frac{ 1}{20} → frac{ 1}{B} = frac{4}{20} → 4B = 20 → B = 5) Bingo!
A = 4 and B = 5 → A + B = 9

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